Electroplating of metal nanotubes and nanowires in a high aspect-ratio nanotemplate

Ordered metal (Co, Pt, and CoPt alloy) nanotube and nanowire structures were fabricated by a simple electroplating method in high aspect-ratio anodic aluminum oxide (AAO) membrane. The growth rate in pulse mode is always larger than that in constant-current mode, which represents that diffusion limitation exists in this electroplating condition. It is also found that the sputtered Au layer structure could influence the electroplating. Traditional nanowires could be fabricated in the template with a uniform Au layer as conducting contact. In case of unblocked AAO membrane, metal electroplating begins from the Au particles which were attached inside the holes during the sputtering step and produces metal nanotubes. Pt and CoPt nanotubes could be easily prepared by this method and might be applied as catalyst and magnetic material.     

Tracking thermally-activated transformations in a nanostructured metal/oxide/metal system

We present experimental and theoretical evidence of sequential redox processes and structural transformations occurring by increasing temperature in a metal/oxide/metal system obtained via deposition of Fe atoms onto a z'-TiO(1.25)/Pt(111) ultrathin film in UHV. The initial reduction of the z'-TiO(x) phase by Fe at room temperature is followed by Fe diffusion and partial penetration into the substrate at intermediate temperatures. This triggers the formation of a bi-component material in which mixed FeO/TiO(2) nanoislands coexist on a h-TiO(1.14) ultrathin film, notably restructured (from rectangular to hexagonal) and reduced (from Ti : O = 1 : 1.25 to 1 : 1.14) with respect to the original TiO(1.25) phase. Further heating recovers the pristine z'-TiO(x) phase while Fe completely dissolves into the substrate.     

Probing interfacial characteristics of rubrene/pentacene and pentacene/rubrene bilayers with soft X-ray spectroscopy

The electronic structure of rubrene/pentacene and pentacene/rubrene bilayers has been investigated using soft X-ray absorption spectroscopy, resonant X-ray emission spectroscopy, and density-functional theory calculations. X-ray absorption and emission measurements reveal that it has been possible to alter the lowest unoccupied and the highest occupied molecular orbital states of rubrene in rubrene/pentacene bilayer. In the reverse case, one gets p* molecular orbital states originating from the pentacene layer. Resonant X-ray emission spectra suggest a reduction in the hole-transition probabilities for the pentacene/rubrene bilayer in comparison to reference pentacene layer. For the rubrenepentacene structure, the hole-transition probability shows an increase in comparison to the rubrene reference. We also determined the energy level alignment of the pentacene-rubrene interface by using X-ray and ultraviolet photoelectron spectroscopy. From these comparisons, it is found that the electronic structure of the pentacene-rubrene interface has a strong dependence on interface characteristics which depends on the order of the layers used.     

Molecular dynamics simulation of a water/metal interface

First results of a molecular dynamics study of a water/metal interface, lasting 3.3 ps at an average temperature of 294 K, are reported. The basic periodic box contains 216 water molecules and a crystal slab of 550 platinum atoms with (100) surface planes. A combination of a Lennard-Jones potential between centers of mass and a Coulomb potential arising from dielectric interactions of the water charge distribution with the metal is employed for the water-wall interaction, the ST2 model for the water-water, and a nearest-neighbour harmonic potential for the platinum-platinum interactions. Considerable adsorption at the interface together with a drastic change of the water structure is observed.     

Molecular switch on a metal surface

We report a theoretical study for the conformational switching of molecules on Au(111) surface in the presence of an applied electric field. Ab initio calculations for N-(2-mercaptoethyl)benzamide indicate that this molecule, when adsorbed, can exist as two stable conformers of nearly equal energies, but the dipoles point in reverse directions with respect to the surface. An electric field can be used to "switch" one conformer to the other, and during this process, there is an abrupt change in the height of the molecule from the surface. This change is expected to cause a conductance switching in the system. Further calculations for N-(2-mercaptoethyl)-4-phenylazobenzamide suggest that the experimentally observed phase switching of this molecule is associated with a conformational change accompanied by dipole reversal.     

Chemical assembly of a titanium oxide layer on microporous silica

Russian Journal of General Chemistry - The chemical assembly of a titanium oxide coating on a regular microporous silica surface by the atomic layer deposition method was considered. The change in...     

Molecular assembly of a pyridine functionalized janusarene

We describe a janusarene derivative PyJ, which forms micrometer-scale one-dimensional metallosupramolecular polymer through coordination driven self-assembly. PyJ is a well-preorganized dodecatopic pyridyl ligand built on a hexaphenylbenzene platform. The two-face structural feature of PyJ allows for a delicate control over multiple Py-Ag⁺-Py coordination interactions, leading to assembled structure of PyJ-Ag⁺, which was characterized by dynamic light scattering, atomic for...     

Molecular assembly of a 3D-ordered multilayer

Combining strong metal-ligand coordination and pi-pi interactions affords a 3D-ordered molecular-based multilayer. The organization of the assembly is apparent from the optical properties and X-ray reflectivity.     

Separation of metal ions on a modified aluminium oxide

The possibility of application of a sulpho-derivative of an aromatic organic complexing agent for separation of cations on aluminium oxide has been investigated. Alumina modified with Nitroso-R salt is used for recovery of cobalt from a tap water and for selective separation of palladium from rhodium.     

Solvent/additive-free synthesis of porous/zeolitic metal azolate frameworks from metal oxide/hydroxide

Porous/zeolitic metal azolate frameworks may be efficiently prepared, with water as the only byproduct, by heating a mixture of metal oxide/hydroxide and azole ligand.     

Molecular electrodes at the exposed edge of metal/insulator/metal trilayer structures

Producing reliable electrical contacts of molecular dimensions has been a critical challenge in the field of molecule-based electronics. Conventional thin film deposition and photolithography techniques have been utilized to construct novel nanometer-sized electrodes on the exposed vertical plane on the edge of a thin film multilayer structure (metal/insulator/metal). Via thiol surface attachment to metal leads, an array of paramagnetic, cyanide-bridged octametal complexes, [(pzTp)FeIII(CN)3]4[NiII(L)]4[O3SCF3]4 (1) [(pzTp) = tetra(pyrazol-1-yl)borate; L = 1-S(acetyl)tris(pyrazolyl)decane], were covalently linked onto the electrodes forming a dominant conduction pathway. A series of molecule-based devices were fabricated using Ni, NiFe, Ta, and Au as metal electrodes separated by insulating Al2O3 spacers, followed by treatment with 1. A series of control experiments were also performed to demonstrate that the conduction path was through tethered metal clusters. The molecular current was analyzed via the Simmons tunnel model, and calculations are consistent with electron tunneling through the alkane ethers to the central metal core. With a Ni/Al2O3/Au molecular electrode, the tether binding was found to be reversible to the top Au layer, allowing for a new class of chemical detection based on the steric bulk of coordinating analytes to disconnect the molecular current path. Simple and economical photolithography/liftoff/self-assembly fabrication techniques afford robust molecular junctions with high reproducibility (>90%) and long operational lifetimes (>1 year).     

Enhanced charge transfer by phenyl groups at a rubrene/C60 interface

Exciton dynamics at an interface between an electron donor, rubrene, and a C(60) acceptor is studied by nonadiabatic quantum molecular dynamics simulation. Simulation results reveal an essential role of the phenyl groups in rubrene in increasing the charge-transfer rate by an order-of-magnitude. The atomistic mechanism of the enhanced charge transfer is found to be the amplification of aromatic breathing modes by the phenyl groups, which causes large fluctuations of electronic excitation energies. These findings provide insight into molecular structure design for efficient solar cells, while explaining recent experimental observations.     

Analysis of various metal oxide/organohalide-based flame retardants

The mechanism of evaporation of various metal oxides and the formation and evaporation of metal halides in the presence of chlorine-containing compounds have been studied by complex thermal analysis including atomic absorption measurement of the evolved species. The retardation process in the case of the MoO₃+ and the ZnO + system and that for Al₂O₃ ·3H₂O has been discussed.

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Zusammenfassung Der Verdampfungsmechanismus verschiedener Metalloxide sowie Bildung und Verdampfen von Metallhalogeniden im Falle von chlorhaltigen Additiven wurde untersucht. Es wurden Messungen mittels komplexer Thermoanalyse einschließlich von Atomabsorptionsuntersuchungen der entweichenden Stoffe durchgeführt. Die Hemmungsprozesse von MoO₃ + Halogen, ZnO +Halogen und Al₂O₃ · 3H₂O werden besprochen.

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, . , - . MoO₃ + , ZnO + l₂O₃·₂.

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The authors are indebted to Prof. B. Mohai for valuable discussions and suggestions.     

pH-driven assembly of various supported lipid platforms: a comparative study on silicon oxide and titanium oxide

Supported lipid platforms are versatile cell membrane mimics whose structural properties can be tailored to suit the application of interest. By identifying parameters that control the self-assembly of these platforms, there is potential to develop advanced biomimetic systems that overcome the surface specificity of lipid vesicle interactions under physiological conditions. In this work, we investigated the adsorption kinetics of vesicles onto silicon and titanium oxides as a function of pH. On each substrate, a planar bilayer and a layer of intact vesicles could be self-assembled in a pH-dependent manner, demonstrating the role of surface charge density in the self-assembly process. Under acidic pH conditions where both zwitterionic lipid vesicles and the oxide films possess near-neutral electric surface charges, vesicle rupture could occur, demonstrating that the process is driven by nonelectrostatic interactions. However, we observed that the initial rupturing process is insufficient for propagating bilayer formation. The role of electrostatic interactions for propagating bilayer formation differs for the two substrates; electrostatic attraction between vesicles and the substrate is necessary for complete bilayer formation on titanium oxide but is not necessary on silicon oxide. Conversely, in the high pH regime, repulsive electrostatic interactions can result in the irreversible adsorption of intact vesicles on silicon oxide and even a reversibly adsorbed vesicle layer on titanium oxide. Together, the results show that pH is an effective tool to modulate vesicle-substrate interactions in order to create various self-assembled lipid platforms on hydrophilic substrates.     

Electrochemical impedance simulation of a metal oxide heterostructure/electrolyte interface: A review

The results of an analysis of the literature data obtained when investigating processes of charge transfer at interfaces of heterostructures formed by various methods, including the high-energy methods, are presented in this paper. The performed investigation of oxide layers at the titanium surface, with use made of impedance spectroscopy data made it possible to reveal the nature and influence of some processes and factors on the charge transfer mechanism realized at a metal oxide heterostructure/electrolyte interface. Simulating an oxide/electrolyte interface gives one a chance to identify, in a spectrum, the responses that characterize the behavior of porous and poreless layers, as well as the responses that are due to the space-charge region formed in the oxide material and to the corrosion and diffusion processes.     

PAN-based activated carbon nanofiber/metal oxide composites for CO2 and CH4 adsorption: influence of metal oxide

In the present study, we successfully prepared two different electrospun polyacrylonitrile (PAN) based-activated carbon nanofiber (ACNF) composites by incorporation of well-distributed Fe₂O₃ and Co₃O₄ nanoparticles (NPs). The influence of metal oxide on the structural, morphological, and textural properties of final composites was thoroughly investigated. The results showed that the morphological and textural properties could be easily tuned by changing the metal oxide NPs. Even though, the ACNF composites were not chemically activated by any activation agent, they presented relatively high surface areas (S_BET) calculated by Brunauer–Emmett–Teller (BET) equation as 212.21 and 185.12 m²/g for ACNF/Fe₂O₃ and ACNF/Co₃O₄ composites, respectively. Furthermore, the ACNF composites were utilized as candidate adsorbents for CO₂ and CH₄ adsorption. The ACNF/Fe₂O₃ and ACNF/Co₃O₄ composites resulted the highest CO₂ adsorption capacities of 1.502 and 2.166 mmol/g at 0 °C, respectively, whereas the highest CH₄ adsorption capacities were obtained to be 0.516 and 0.661 mmol/g at 0 °C by ACNF/Fe₂O₃ and ACNF/Co₃O₄ composites, respectively. The isosteric heats calculated lower than 80 kJ/mol showed that the adsorption processes of CO₂ and CH₄ were mainly dominated by physical adsorption for both ACNF composites. Our findings indicated that ACNF-metal oxide composites are useful materials for designing of CO₂ and CH₄ adsorption systems.     

Adsorptive characteristics of some metal ions on chitosan/zirconium phosphate/silica decorated graphene oxide

Journal of Radioanalytical and Nuclear Chemistry - Graphene oxide/chitosan/zirconiumphosphate/silicate (GO/CS/ZrP/Si) as a novel nano-composite has highly adsorption of 134Cs, 60Co, 152, 154Eu and...